1. Field of the Invention
The invention relates to a rotor for a small electric motor, in particular for a back-geared motor for automotive use, such as a window raising device of the type comprising, on a shaft, an armature, a current collector and an endless screw produced integrally with the shaft.
2. Description of the Prior Art
For such rotors it is necessary to use shafts having a sufficient diameter to be able to produce the endless screw in one piece and to provide the shaft with a good degree of linearity while the back-geared motor is operating. When winding the armature, the path of the turns of the armature winding at the bottom of the armature slots, when passing from one slot to another, follows the outside of the shaft, the diameter of which is greater than that which would allow a line connecting the base of two slots receiving the same turn of the winding to be straight as a result of which the spatial requirement of the winding on both sides of the armature increases more rapidly than the slots are filled, this filling then being limited, as is the efficiency of the back-geared motor, for a given amount of space.